Thursday, August 2, 2012

3D printed lower receiver for an AR-15 assault rifle.This is the only legally regulated component of the weapon.

It's hard not to like 3D printing. It allows you to transform nearly any 3D form you can draw on the computer into a physical object with a mere push of a button - literally. It also implies a completely alternative way goods might be delivered to consumers, manufactured, or customized to each individual. When your inventory and shipping costs are zero, and your manufacturing volume for any particular model is 1, many traditional assumptions about the economics of manufacturing are no longer valid.

I have no shortage of enthusiasm for that vision. But, there are some significant challenges to overcome before this will become a dominate way people purchase products. So, this transition will not likely occur very quickly.
However, I do watch the space of 3D printing and CNC fabrication with fascination, trying to understand where/when it will have dramatic effects on the manufacture of consumer goods. The object pictured above is a startling example, and may have a significant impact on the public discourse of tools like consumer 3D printing.

It is a 3D printed lower receiver for an AR-15 assault rifle based on the original file on Thingiverse. The version I printed is modified so it can print in two pieces on the smaller bed of my printer and has been made intentionally non-functional. But, this person printed one, assembled the full weapon, and successfully tested it with real ammunition. Apparently, fairly little stress is placed on the lower receiver during firing with most of the energy contained by the metal chambers of the upper receiver.

I find this object fascinating.

The lower receiver is the only component of the AR-15 assault rifle that is regulated by federal law as a "gun". If you disassemble a gun, it has many parts. Each part alone is quite harmless, such as the barrel, the grip, the magazine, the shoulder stock. So, which of the many parts actually constitutes the "gun" and is illegal to sell without a license? the lower receiver - which is like the body frame that holds all the parts together. Every other component you can legally purchase online and have mailed directly to your door step, no background check, no registration. But without the lower receiver, the gun would just fall apart and never be able to fire a round. This is the one part that is illegal to sell without a license, should have a serial number on it, and be registered according to local, state, and federal law.

What happens when the one part of the gun that is so intensely regulated, monitored, and the subject of so much national debate and law-enforcement man power, can simply be downloaded off the internet and printed? An individual sitting in front of a computer, can legally order all of the components of an AR-15 (except the lower receiver), order a 3D printer, download a file, push a button, and within a few hours assemble a fully operational unregistered assault rifle in broad daylight without having to resort to illicit or underground suppliers. What happens if they print 10 of them? 100? While it is definitely illegal to sell the parts without a license, the laws regarding home-built weapons for personal use are much less clear and may vary by locality - so, it is your responsibility to check with your local and state laws before you consider printing one of these.

As with any new technology, it can be used for good as well as evil. This is no different here and is not very surprising. However, what fascinates me is that this little piece of plastic, which was so trivial to make using a 3D printer, completely undermines centuries of debate, and fighting, and lobbying surrounding gun control regulation. In my opinion, this a radical example how technology changes faster than our social and political culture can adapt. As the quality of tools like 3D printing gradually mature and become common place and these models are improved, this tension will only increase. These are interesting times.

5 comments:

The area around the takedown pin is a stress point, and is where Haveblue's lower delaminated, and where the guy who carved a lower out of wood's split. A practical version of a printed lower receiver needs a metal tube there to take load. (There are commercial injection molded plastic AR-15 lowers, they're quite cheap and work well)

Also note: the lower is the regulated part for the AR-15, but this isn't true for many other weapons. (For civilian AK-pattern rifles and FN FALs, the upper receiver is the regulated part-- a much more complicated assembly that bears full recoil forces, and can't be made out of conventional thermoplastics.) The most likely fallout from this 3d printing thing is probably just an ATF ruling that makes the upper receiver the regulated part.

A 3D printer isn't the first ever tool that can produce weapons at home, although it might take less skill than most others. But I'm not sure that I'm any more comfortable with skilled machinists building weapons at home than I am with people of other professions doing it.

Maybe bullet control is the way to go?

But the fact of the matter is that regulating anything that people can make themselves is hard to do (example: household grow ops), and most things that can be manufactured economically in a factory can be manufactured labour-intensively at home.

It is inaccurate to call an AR-15 an assault rifle. That is a term of art, specifically refering to a rifle that is capable of select-fire (which is to say, pull trigger once, and have more than one cartridge be fired), amongst other things. The AR part of the name comes from the original manufacturer, Armalite, indicating it's Armalite Rifle model 15.

It's interesting to note that nearly every rifle commonly commercially available resembles a military firearm. The biggest exception I can think of is specialized target shooting rifles, as used in the competition whose symbol is made of multiple interlocking rings.

There is no US federal requirement for registration of long arms, with the exception of NFA items. Some localities require registration of certain long arms, based on the fact that they have a certain number of features that the drafters of the local laws found scary (such as grenade launcher and bayonet lugs). Serial numbers are required to be placed on firearms by FFL manufacturers, but no such requirement exists on private manufacturers for personal use. It's still a good idea to put one on, and I could see embedding it into the STL file you use such that it's done as part of the printing.

The regulated serialized part is generally the reciever, or some portion of the reciever. It has to be consistant between different manufacturers of the same type of firearm (so you couldn't decide that the upper of your AR-15 compatible firearm was the serialized bit). Some other firearms use the upper, others still use the right side plate of the receiver.

Bullet control is a fairly asinine idea, and is arguably unconstitutional (no one's yet been stupid enough to try and pass such a stupid law). I know that when I'm practicing, I can easily blow through over 500 rds in a single range session. This probably also says something about news reportings crowing about finding x thousand rounds in someone's house.

It will empower people. And with more power comes more responsability. It will force them to think for themselves instead of obeying to a law. This is good. It won't come without broken eggs but nothing is free.

I've heard the argument about being able to "print guns" and other illegal items. (usually within the context of printing a gun within a country where guns are illegal, such as many of the European countries).

Honestly though this isn't really new. most CNC machines are fully capable of milling real metal gun parts, and they don't require any more expertise as a 3D printer. The instructions for machining the "illegal parts" are and have been availble online for quite some time now.

granted CNC machines are more expensive than a 3D printer, but you can buy or build a CNC capable of this for only about 2-3 times the cost of a plastics printer.

At the end of the day if someone really wants to do something, there is ultimately very little you can do to stop them.

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About Me

I am currently a Technical Program Lead in the Advanced Technology and Projects (ATAP) group at Google. Previously, I worked at Google X, and Microsoft Applied Sciences as core contributor to the Xbox Kinect. In 2008, I graduated from Carnegie Mellon University with a PhD in Human-Computer Interaction. My research interests are in exploring novel interface technology that can influence the lives of many people. My main website can be found at johnnylee.net